Localized Destruction, Possibly Broken?

I got lucky enough to pull this PM2 card the other day.

If I have less than 6 Improved Gems or 0 creatures in play, this card casts and does jack-squat...pretty lame for a masterpiece card.
To me, and at least a few others, the text reads as if "Destroy all opposing creatures" will always trigger.

Is it broken, or is the text misleading?
If the "Destroy all opposing creatures" effect is dependent on the thennable, then it should indicate that.

Right now, it's a pretty lame masterpiece.